From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Experimental specifications for the 'Goshawk' 11 'B' Type ignition coil, detailing changes to winding wire for improved insulation.
| Identifier | ExFiles\Box 45\4\ Scan008 | |
| Date | 2nd February 1922 | |
| RMC. C. to Sft.{Mr Swift} Sft.{Mr Swift} EFC. Sft.{Mr Swift} for Mr. Brock W.C. X.4079a EXPERIMENTAL BY/WER9/HF{H. W. Frost - Coachwork Inspector}28. 2. 22. X. 4079c - "GOSHAWK" 11. COIL FOR BATTERY IGNITION "B" TYPE. The works have recently had an odd coil or two returned from service on 40/50 Chassis. Examination has shewn that these Coils have broken down on the primary winding due to poor insulation. These occasional failures suggest that a more robust insulation is required on the wire of which the primary winding is wound. After inspecting samples we have agreed that the best thing to do is to use enamel covered and S.C.C. wire (total insulation thickness .008) instead of D.S.C. Wire (total insulation thickness .004) as at present used on the Ignition Coils for the 40/50 Chassis. To accommodate the increased overall diameter of primary winding we must sacrifice a number of turns of the secondary winding. This EFC has agreed to. Will you therefore have three or four Ignition Coils made up to L.O.P. D.50210 but wound in accordance with the following:- Primary Winding. This should consist of 6 layers - 300 turns of 20 S.W.G. (.036) enamel covered and S.C.C. high conductivity copper wire - length per coil = 24 yds, weight = 5 1/2 ozs. Secondary Winding. This should consist of as many turns as it is possible to wind on of 43 S.W.G. (.0036) enamel coated wire. To enable the Experimental Dept., to build the above coils will the C.C. kindly order the following wire:- 4 lbs of 20 S.W.G. (.036) enamel covered S.C.C. High Conductivity copper wire overall diameter = .044. RECEIVED 1 MAR 1922 PH BY/WER. WER | ||